The major objectives of this project are: (1) to identify and study virus-specific immune effector mechanisms which influence the establishment, course and outcome of experimental murine viral infections, particularly those which have the potential to cause CNS disease; (2) to correlate whole animal observations with quantitative in vitro measurements of virus-specific immune functions; (3) to define the conditions in which certain viral infections preferentially lead either to cellular or humoral virus-specific immune responses, and (4) to use various immunosuppressive treatments which ablate one or more immune effector functions in order to determine the relative contributions of the responses to host recovery.